Pub Date : 2020-10-19DOI: 10.6001/chemija.v31i4.4320
Aušra Čiuladienė, A. Kareiva, R. Raudonis
Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, 24 Naugarduko Street, 03225 Vilnius, Lithuania This study focuses on the characterization of cinnabar, red lead and realgar paints, since the red colour was very often used for the illuminations and rubrics of medieval manuscript. The commercial pigments (cinnabar (HgS), red lead (Pb3O4), realgar (As4S4)) and binding media (gum Arabic, fish and parchment glue) were used for the preparation of analogous to historical paints. This work is on-going and at this stage, the resulting red paint samples were analysed to create a short data library that could be used to describe the various red paints and their compositions. The obtained paints were characterized before and after accelerated aging using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD) and thermal (TG/DSC) analysis techniques. These results of versatile characterization are useful to develop red paint guidelines for the storage and how they affect current and future conservation of these objects.
{"title":"From model to artefact: Versatile characterization of cinnabar, red lead and realgar red paints for rubrics and miniatures","authors":"Aušra Čiuladienė, A. Kareiva, R. Raudonis","doi":"10.6001/chemija.v31i4.4320","DOIUrl":"https://doi.org/10.6001/chemija.v31i4.4320","url":null,"abstract":"Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, 24 Naugarduko Street, 03225 Vilnius, Lithuania This study focuses on the characterization of cinnabar, red lead and realgar paints, since the red colour was very often used for the illuminations and rubrics of medieval manuscript. The commercial pigments (cinnabar (HgS), red lead (Pb3O4), realgar (As4S4)) and binding media (gum Arabic, fish and parchment glue) were used for the preparation of analogous to historical paints. This work is on-going and at this stage, the resulting red paint samples were analysed to create a short data library that could be used to describe the various red paints and their compositions. The obtained paints were characterized before and after accelerated aging using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD) and thermal (TG/DSC) analysis techniques. These results of versatile characterization are useful to develop red paint guidelines for the storage and how they affect current and future conservation of these objects.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":"31 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41432365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-19DOI: 10.6001/chemija.v31i4.4317
E. Vernickaitė, M. Lelis, N. Tsyntsaru, V. Pakštas, H. Cesiulis
5 Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania The possibility to use highly saturated acetate bath to electrodeposit the mixed-phase materials containing Mo oxides has been investigated. The XRD characterization revealed that the as-deposited coatings are amorphous and consist only of MoO2 and MoO3 phases without traces of metallic Mo phase. This statement has been supported by XPS measurements, which reveal the presence of three different molybdenum oxidations states in electrodeposits: Mo4+, Mo5+ and Mo6+. It was found that the Mo6+ state prevails with 41% of total contribution, whilst Mo5+ and Mo4+ contribute to 28 and 31%, respectively. The deposits retain an amorphous structure up to 800°C; while molybdenum at this temperature is predominantly oxidized to the Mo6+ state (91%). These results, coupled to those of SEM and EDS, revealed that concentrated acetate bath could be used mainly for the formation of the mixed valence molybdenum oxide film unlike to the deposition of the metallic Mo phase.
{"title":"XPS studies on the Mo oxide-based coatings electrodeposited from highly saturated acetate bath","authors":"E. Vernickaitė, M. Lelis, N. Tsyntsaru, V. Pakštas, H. Cesiulis","doi":"10.6001/chemija.v31i4.4317","DOIUrl":"https://doi.org/10.6001/chemija.v31i4.4317","url":null,"abstract":"5 Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania The possibility to use highly saturated acetate bath to electrodeposit the mixed-phase materials containing Mo oxides has been investigated. The XRD characterization revealed that the as-deposited coatings are amorphous and consist only of MoO2 and MoO3 phases without traces of metallic Mo phase. This statement has been supported by XPS measurements, which reveal the presence of three different molybdenum oxidations states in electrodeposits: Mo4+, Mo5+ and Mo6+. It was found that the Mo6+ state prevails with 41% of total contribution, whilst Mo5+ and Mo4+ contribute to 28 and 31%, respectively. The deposits retain an amorphous structure up to 800°C; while molybdenum at this temperature is predominantly oxidized to the Mo6+ state (91%). These results, coupled to those of SEM and EDS, revealed that concentrated acetate bath could be used mainly for the formation of the mixed valence molybdenum oxide film unlike to the deposition of the metallic Mo phase.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42863670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-19DOI: 10.6001/chemija.v31i4.4326
Audrius Sadaunykas, Audrius Zolumskis, Audrius Markevičius, E. Naujalis
Metrology Department, State Research Institute Center for Physical Sciences and Technology, 231 Savanorių Avenue, 02300 Vilnius, Lithuania The objective of this work was to design, construct and test the sample focusing and concentration enrichment device for gas chromatography. The device was based on four metal rings, between which a capillary column and two wire heaters were placed. The metal rings were connected to each other and cooled down using liquid nitrogen. The column was connected to the gas chromatography system using a heated transfer line. The research was conducted on how the length of the cooled column influences focusing and enrichment capabilities of the system. It was found that the analytes were focused better by using a longer cooled part of the column. The longer cooled column was also able to retain a greater volume of the analytes, injected consecutively. By using the 95 cm cooled column length, it was possible to retain 20 injections and detect a 20 times bigger peak area. By changing the temperature of the cooling zone, it was also observed that peak symmetry is heavily dependent on it. Lower cooled zone temperatures produced narrower and more symmetrical peaks.
{"title":"On-column cryofocusing and analyte enrichment device for gas chromatography systems","authors":"Audrius Sadaunykas, Audrius Zolumskis, Audrius Markevičius, E. Naujalis","doi":"10.6001/chemija.v31i4.4326","DOIUrl":"https://doi.org/10.6001/chemija.v31i4.4326","url":null,"abstract":"Metrology Department, State Research Institute Center for Physical Sciences and Technology, 231 Savanorių Avenue, 02300 Vilnius, Lithuania The objective of this work was to design, construct and test the sample focusing and concentration enrichment device for gas chromatography. The device was based on four metal rings, between which a capillary column and two wire heaters were placed. The metal rings were connected to each other and cooled down using liquid nitrogen. The column was connected to the gas chromatography system using a heated transfer line. The research was conducted on how the length of the cooled column influences focusing and enrichment capabilities of the system. It was found that the analytes were focused better by using a longer cooled part of the column. The longer cooled column was also able to retain a greater volume of the analytes, injected consecutively. By using the 95 cm cooled column length, it was possible to retain 20 injections and detect a 20 times bigger peak area. By changing the temperature of the cooling zone, it was also observed that peak symmetry is heavily dependent on it. Lower cooled zone temperatures produced narrower and more symmetrical peaks.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43919345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-19DOI: 10.6001/chemija.v31i4.4321
M. Zhyhailo, I. Yevchuk, M. Yatsyshyn, S. Korniy, O. Demchyna, R. Musiy, R. Raudonis, A. Zarkov, A. Kareiva
4 Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, 24 Naugarduko Street, 03225 Vilnius, Lithuania The development of proton conductive polyacrylate membranes based on acrylonitrile, sodium 4-vinylbenzenesulfonate, acrylic acid, ethylene glycol dimethacrylate and hybrid polyacrylate/silica membranes is reported in this article. Polyacrylate membranes were synthesized via UV-initiated copolymerization; for the synthesis of polyacrylate/silica membranes 3-methacryloxypropyl trimethoxysilane-based sol–gel system was introduced into the polymerizing mixture.
{"title":"Preparation of polyacrylate/silica membranes for fuel cell application by in situ UV polymerization","authors":"M. Zhyhailo, I. Yevchuk, M. Yatsyshyn, S. Korniy, O. Demchyna, R. Musiy, R. Raudonis, A. Zarkov, A. Kareiva","doi":"10.6001/chemija.v31i4.4321","DOIUrl":"https://doi.org/10.6001/chemija.v31i4.4321","url":null,"abstract":"4 Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, 24 Naugarduko Street, 03225 Vilnius, Lithuania The development of proton conductive polyacrylate membranes based on acrylonitrile, sodium 4-vinylbenzenesulfonate, acrylic acid, ethylene glycol dimethacrylate and hybrid polyacrylate/silica membranes is reported in this article. Polyacrylate membranes were synthesized via UV-initiated copolymerization; for the synthesis of polyacrylate/silica membranes 3-methacryloxypropyl trimethoxysilane-based sol–gel system was introduced into the polymerizing mixture.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49022916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-19DOI: 10.6001/chemija.v31i4.4324
A. Judžentienė
The paper reviews already (in the past fifteen years) published data from research articles on essential oils (EOs) and their biological properties (such as antioxidant, antifungal, anti-inflammatory and toxic activity) of marsh rosemary (Rhododendron tomentosum (Stokes) Harmaja (ex Ledum palustre Linnaeus, Ericaceae Juss.) growing wild in Lithuania. Rh. tomentosum is a perennial woody shrub (up to 1 m in height) with evergreen leaves and small white or white-pink sticky flowers grouped in racemes. The plant emits a strong specific smell that affects the central nervous system, and may cause nausea, headache or aggressive behaviour to some people. Only one species of the plant (ex L. palustre var. palustre) grows in Lithuania, mainly forming colonies in limited areas over all the territory. Marsh rosemary are widely used in folk medicine and homeopathy for treatment of various sickness, externally and internally as well. Most applications of Rh. tomentosum and pharmacological properties have been validated by scientific researches. In Lithuania, the plant is used for healing rheumatism, different pains, insect bites, eczema and other skin problems, infections, bronchitis, asthma, cold, tuberculosis, to block bleeding, etc. Rhododendron tomentosum H. (ex Ledum palustre L.) plants, the essential oils (EOs) of which are already investigated, were collected mostly in the Eastern part of the country (Rokiškis, Utena, Vilnius and Šalčininkai districts). Monoterpene hydrocarbons, p-cymene, myrcene and limonene, bicyclic monoterpenoid ascaridole and oxygenated sesquiterpenes, ledol, palustrol and cyclocolorenone isomers, were found to be principal compounds in the investigated EOs. Some oils contained appreciable quantities of heterocyclic compound lepalol. Most of the oils could be attributed to the ledol+palustrol or ledol+palustrol+ascaridole chemotype. Antifungal activity of Rh. tomentosum EOs was evaluated by several different techniques: against Penicillium cyclopium Westling, Trichoderma harzianum Rifai and Candida parapsilosis using an agar diffusion method; and amperometricaly, using Saccharomyces cerevisiae yeast-modified electrodes. Anti-inflammatory activity of Lithuanian marsh rosemary EOs has been revealed by subcutaneous carrageenan injection-induced hind paw oedema tests. However, antioxidant activity (tests using ABTS˙+, DPPH˙ and TROLOX) and toxic properties (against brine shrimp (Artemia sera) larvae) of Rh. tomentosum EOs were summarized.
本文综述了近15年来发表的关于立陶宛野生沼泽迷迭香(Rhododendron tomentosum (Stokes) Harmaja (ex Ledum palustre Linnaeus, Ericaceae Juss.)精油及其生物学特性(如抗氧化、抗真菌、抗炎和毒性活性)的研究数据。Rh。毛毡草是一种多年生木本灌木(可达1米高)，有常绿的叶子和小的白色或白粉红色的粘性花，簇生在总状花序中。这种植物散发出一种强烈的特殊气味，会影响中枢神经系统，并可能引起恶心、头痛或某些人的攻击行为。这种植物只有一种(除L. palustre var. palustre)生长在立陶宛，主要在所有领土上的有限地区形成殖民地。迷迭香被广泛用于民间医学和顺势疗法中，用于治疗各种疾病，无论是外用还是内用。Rh的大多数应用。经科学研究证实其药理特性。在立陶宛，这种植物被用来治疗风湿病、各种疼痛、昆虫叮咬、湿疹和其他皮肤问题、感染、支气管炎、哮喘、感冒、肺结核、止血等。毛毛杜鹃花(ex Ledum palustre L.)植物的精油(EOs)已被调查，主要采集于该国东部(Rokiškis、乌特纳、维尔纽斯和Šalčininkai区)。单萜烃、对伞花烃、月桂烯和柠檬烯、双环单萜天冬烯和氧化倍半萜、ledol、palustrol和环环烯酮异构体是所研究的EOs中的主要化合物。有些油含有相当数量的杂环化合物黎麻酚。大部分精油可归因于ledol+palustrol或ledol+palustrol+ascaridole化学型。Rh的抗真菌活性。采用几种不同的技术对绒毛菌进行评价:采用琼脂扩散法对环青霉、哈兹木霉和假丝酵母进行抑菌;在电流计量学上，使用酿酒酵母修饰的电极。通过卡拉胶皮下注射诱导后足水肿试验，揭示了立陶宛沼泽迷迭香的抗炎活性。然而，Rh的抗氧化活性(使用ABTS˙+、DPPH˙和TROLOX进行测试)和毒性(对卤虾(Artemia sera)幼虫)。总结毛囊EOs。
{"title":"Review: Marsh rosemary (Rhododendron tomentosum Harmaja (ex Ledum palustre Linn) growing in Lithuania) essential oils and their properties","authors":"A. Judžentienė","doi":"10.6001/chemija.v31i4.4324","DOIUrl":"https://doi.org/10.6001/chemija.v31i4.4324","url":null,"abstract":"The paper reviews already (in the past fifteen years) published data from research articles on essential oils (EOs) and their biological properties (such as antioxidant, antifungal, anti-inflammatory and toxic activity) of marsh rosemary (Rhododendron tomentosum (Stokes) Harmaja (ex Ledum palustre Linnaeus, Ericaceae Juss.) growing wild in Lithuania. Rh. tomentosum is a perennial woody shrub (up to 1 m in height) with evergreen leaves and small white or white-pink sticky flowers grouped in racemes. The plant emits a strong specific smell that affects the central nervous system, and may cause nausea, headache or aggressive behaviour to some people. Only one species of the plant (ex L. palustre var. palustre) grows in Lithuania, mainly forming colonies in limited areas over all the territory. Marsh rosemary are widely used in folk medicine and homeopathy for treatment of various sickness, externally and internally as well. Most applications of Rh. tomentosum and pharmacological properties have been validated by scientific researches. In Lithuania, the plant is used for healing rheumatism, different pains, insect bites, eczema and other skin problems, infections, bronchitis, asthma, cold, tuberculosis, to block bleeding, etc. Rhododendron tomentosum H. (ex Ledum palustre L.) plants, the essential oils (EOs) of which are already investigated, were collected mostly in the Eastern part of the country (Rokiškis, Utena, Vilnius and Šalčininkai districts). Monoterpene hydrocarbons, p-cymene, myrcene and limonene, bicyclic monoterpenoid ascaridole and oxygenated sesquiterpenes, ledol, palustrol and cyclocolorenone isomers, were found to be principal compounds in the investigated EOs. Some oils contained appreciable quantities of heterocyclic compound lepalol. Most of the oils could be attributed to the ledol+palustrol or ledol+palustrol+ascaridole chemotype. Antifungal activity of Rh. tomentosum EOs was evaluated by several different techniques: against Penicillium cyclopium Westling, Trichoderma harzianum Rifai and Candida parapsilosis using an agar diffusion method; and amperometricaly, using Saccharomyces cerevisiae yeast-modified electrodes. Anti-inflammatory activity of Lithuanian marsh rosemary EOs has been revealed by subcutaneous carrageenan injection-induced hind paw oedema tests. However, antioxidant activity (tests using ABTS˙+, DPPH˙ and TROLOX) and toxic properties (against brine shrimp (Artemia sera) larvae) of Rh. tomentosum EOs were summarized.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44087001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-19DOI: 10.6001/chemija.v31i4.4319
Daina Upskuvienė, D. Šimkūnaitė, J. Vaičiūnienė, V. Kepenienė, A. Selskis, L. Tamašauskaitė-Tamašiūnaitė, E. Norkus
State Research Institute Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania In this study, the carbon powder supported gold nanoparticles composites (AuNPs/C) were prepared via the chemical reduction method by employing sodium citrate or a complex mixture of glucose and ascorbic acid as reducing agents in the presence of small amounts of different halide ions (Cl–, Br–, I–). The electrocatalytic activity of the synthesized composites was evaluated for the electro-oxidation of glucose in an alkaline medium using cyclic voltammetry, whereas the morphology and composition of composites were characterized using field emission scanning electron microscopy and inductively coupled plasma optical emission spectroscopy. The electrochemical measurements demonstrate the enhanced electrocatalytic performance of the AuNPs/C composites prepared by the help of different reducing agents coupled with halide ions for the electro-oxidation of glucose as compared to that of composites that were synthesized by the use only of the reducing agents barely. The AuNPs/C composites synthesized with the presence of KCl, KBr or KI additive in the reaction mixture generate the increased glucose electro-oxidation current density values; furthermore, the glucose electro-oxidation potential is shifted to more negative values as compared to those obtained on the synthesized composites without halide additive.
{"title":"Investigation of electro-oxidation of glucose at gold nanoparticles/carbon composites prepared in the presence of halide ions","authors":"Daina Upskuvienė, D. Šimkūnaitė, J. Vaičiūnienė, V. Kepenienė, A. Selskis, L. Tamašauskaitė-Tamašiūnaitė, E. Norkus","doi":"10.6001/chemija.v31i4.4319","DOIUrl":"https://doi.org/10.6001/chemija.v31i4.4319","url":null,"abstract":"State Research Institute Center for Physical Sciences and Technology, 3 Saulėtekio Avenue, 10257 Vilnius, Lithuania In this study, the carbon powder supported gold nanoparticles composites (AuNPs/C) were prepared via the chemical reduction method by employing sodium citrate or a complex mixture of glucose and ascorbic acid as reducing agents in the presence of small amounts of different halide ions (Cl–, Br–, I–). The electrocatalytic activity of the synthesized composites was evaluated for the electro-oxidation of glucose in an alkaline medium using cyclic voltammetry, whereas the morphology and composition of composites were characterized using field emission scanning electron microscopy and inductively coupled plasma optical emission spectroscopy. The electrochemical measurements demonstrate the enhanced electrocatalytic performance of the AuNPs/C composites prepared by the help of different reducing agents coupled with halide ions for the electro-oxidation of glucose as compared to that of composites that were synthesized by the use only of the reducing agents barely. The AuNPs/C composites synthesized with the presence of KCl, KBr or KI additive in the reaction mixture generate the increased glucose electro-oxidation current density values; furthermore, the glucose electro-oxidation potential is shifted to more negative values as compared to those obtained on the synthesized composites without halide additive.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49298019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-19DOI: 10.6001/chemija.v31i3.4293
Benjaminas Valiauga, N. Rouhier, J. Jacquot, N. Čėnas
2 Université de Lorraine, INRAE, IAM, F-54500 Vandoeuvre-les-Nancy, France The fluorescence properties of FAD of Thermotoga maritima thioredoxin reductase (TmTR), taken together with the amino acid sequences and structures of similar TRs, are consistent with the interdomain rotation in the catalysis of TmTR. The standard redox potential of FAD of TmTR, –0.230 V, determined by the reactions with 3-acetylpyridine adenine dinucleotide (APAD+/APADH) redox couple, is close to that of E. coli TR. During the reduction of duroquinone with TmTR, the transient formation of neutral FAD semiquinone, and, possibly, FADH2–NAD + complex was observed. This shows that in spite of obligatory twoelectron (hydride)-transfer between NADH and physiological disulfide oxidants, the FAD cofactor of TmTR may exist under a stable semiquinone form.
2洛林大学，INRAE，IAM，F-54500 Vandoeuvre les Nancy，France海洋热托加硫氧还蛋白还原酶（TmTR）的FAD的荧光性质，连同类似TR的氨基酸序列和结构，与TmTR催化中的结构域间旋转一致。通过与3-乙酰吡啶腺嘌呤二核苷酸（APAD+/APADH）氧化还原对的反应确定的TmTR的FAD的标准氧化还原电位为–0.230 V，与大肠杆菌TR的氧化还原电位接近。在用TmTR还原杜洛醌的过程中，观察到中性FAD半醌的瞬时形成，可能还有FADH2–NAD+复合物。这表明，尽管NADH和生理性二硫化物氧化剂之间存在强制性的二电子（氢化物）转移，但TmTR的FAD辅因子可能以稳定的半醌形式存在。
{"title":"Characterization of redox properties of FAD cofactor of Thermotoga maritima thioredoxin reductase","authors":"Benjaminas Valiauga, N. Rouhier, J. Jacquot, N. Čėnas","doi":"10.6001/chemija.v31i3.4293","DOIUrl":"https://doi.org/10.6001/chemija.v31i3.4293","url":null,"abstract":"2 Université de Lorraine, INRAE, IAM, F-54500 Vandoeuvre-les-Nancy, France The fluorescence properties of FAD of Thermotoga maritima thioredoxin reductase (TmTR), taken together with the amino acid sequences and structures of similar TRs, are consistent with the interdomain rotation in the catalysis of TmTR. The standard redox potential of FAD of TmTR, –0.230 V, determined by the reactions with 3-acetylpyridine adenine dinucleotide (APAD+/APADH) redox couple, is close to that of E. coli TR. During the reduction of duroquinone with TmTR, the transient formation of neutral FAD semiquinone, and, possibly, FADH2–NAD + complex was observed. This shows that in spite of obligatory twoelectron (hydride)-transfer between NADH and physiological disulfide oxidants, the FAD cofactor of TmTR may exist under a stable semiquinone form.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46857165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-19DOI: 10.6001/chemija.v31i3.4285
K. Leinartas, E. Juzeliūnas, L. Staišiūnas, A. Selskis, A. Grigucevičienė, D. Bučinskienė, R. Juškėnas, A. Ručinskienė
Department of Electrochemical Materials Science, Centre for Physical Sciences and Technology, 3 Saulėtekio Avenue, Vilnius, Lithuania Thin Mg–Nb alloy films having a thickness below 1 μm were deposited by magnetron sputtering on glass substrates with Nb concentrations of 4, 26 and 32 at.%. Distribution of the elements within the deposits was identified by a scanning transmission electron microscope (STEM) equipped with a high angle annular dark field (HAADF) detector, which showed on a nanometer scale fine Nb-enriched structures. XRD identified nano-crystallinity of the deposits with grain sizes of the order of tens of nanometers. The corrosion behaviour of the films has been studied in a balanced salt solution, whose pH and ion concentrations were close to those of the human blood plasma. The electrochemical impedance spectroscopy implied a localized corrosion with diffusion limitations within a layer of corrosion products. The corrosion rates were determined in situ by Tafel extrapolation and EIS-derived polarization resistance; both methods provided reliable results for corrosion resistant alloy with ca. one third of Nb. Alloying of Mg with Nb makes it possible to adjust the corrosion activity of the alloy according to biomedical requirements for in vivo applications.
{"title":"Early stages of Mg–Nb alloy corrosion in a balanced salt solution – STEM-HAADF and EIS study","authors":"K. Leinartas, E. Juzeliūnas, L. Staišiūnas, A. Selskis, A. Grigucevičienė, D. Bučinskienė, R. Juškėnas, A. Ručinskienė","doi":"10.6001/chemija.v31i3.4285","DOIUrl":"https://doi.org/10.6001/chemija.v31i3.4285","url":null,"abstract":"Department of Electrochemical Materials Science, Centre for Physical Sciences and Technology, 3 Saulėtekio Avenue, Vilnius, Lithuania Thin Mg–Nb alloy films having a thickness below 1 μm were deposited by magnetron sputtering on glass substrates with Nb concentrations of 4, 26 and 32 at.%. Distribution of the elements within the deposits was identified by a scanning transmission electron microscope (STEM) equipped with a high angle annular dark field (HAADF) detector, which showed on a nanometer scale fine Nb-enriched structures. XRD identified nano-crystallinity of the deposits with grain sizes of the order of tens of nanometers. The corrosion behaviour of the films has been studied in a balanced salt solution, whose pH and ion concentrations were close to those of the human blood plasma. The electrochemical impedance spectroscopy implied a localized corrosion with diffusion limitations within a layer of corrosion products. The corrosion rates were determined in situ by Tafel extrapolation and EIS-derived polarization resistance; both methods provided reliable results for corrosion resistant alloy with ca. one third of Nb. Alloying of Mg with Nb makes it possible to adjust the corrosion activity of the alloy according to biomedical requirements for in vivo applications.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44473433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-19DOI: 10.6001/chemija.v31i3.4291
A. Nemeikaitė-Čėnienė, J. Šarlauskas, V. Jonušienė, Lina Misevičienė, A. Marozienė, A. Yantsevich, N. Čėnas
4 Institute of Bioorganic Chemistry, NAS of Belarus, Kuprevicha 5/2, BY-220072 Minsk, Belarus Frequently, the aerobic mammalian cell cytotoxicity of nitroaromatic compounds (ArNO2) increases with their single-electron reduction potential (E7), thus reflecting the relationship between their enzymatic single-electron reduction rate and E7. This shows that the main factor of ArNO2 cytotoxicity is redox cycling and oxidative stress. In this work, we found that the reactivity of a series of nitrobenzenes, nitrofurans and nitrothiophenes towards single-electron transferring NADPH:cytochrome P-450 reductase and adrenodoxin reductase/adrenodoxin increases with their E7. However, their cytotoxicity in mouse hepatoma MH22a and human colon carcinoma HCT-116 cells exhibited a poorly expressed dependence on E7. The correlations were significantly improved after the introduction of compound octanol/water distribution coefficient at pH 7.0 (log D) as a second variable. This shows that the lipophilicity of ArNO2 enhances their cytotoxicity. The inhibitors of cytochromes P-450, α-naphthoflavone, isoniazid and miconazole, and an inhibitor of DT-diaphorase, dicoumarol, in most cases decreased the cytotoxicity of several randomly chosen compounds. This shows that the observed cytotoxicity vs E7 relationships in fact reflect the superposition of several cytotoxicity mechanisms.
{"title":"QSARs in prooxidant mammalian cell cytotoxicity of nitroaromatic compounds: the roles of compound lipophilicity and cytochrome P-450- and DT-diaphorase-catalyzed reactions","authors":"A. Nemeikaitė-Čėnienė, J. Šarlauskas, V. Jonušienė, Lina Misevičienė, A. Marozienė, A. Yantsevich, N. Čėnas","doi":"10.6001/chemija.v31i3.4291","DOIUrl":"https://doi.org/10.6001/chemija.v31i3.4291","url":null,"abstract":"4 Institute of Bioorganic Chemistry, NAS of Belarus, Kuprevicha 5/2, BY-220072 Minsk, Belarus Frequently, the aerobic mammalian cell cytotoxicity of nitroaromatic compounds (ArNO2) increases with their single-electron reduction potential (E7), thus reflecting the relationship between their enzymatic single-electron reduction rate and E7. This shows that the main factor of ArNO2 cytotoxicity is redox cycling and oxidative stress. In this work, we found that the reactivity of a series of nitrobenzenes, nitrofurans and nitrothiophenes towards single-electron transferring NADPH:cytochrome P-450 reductase and adrenodoxin reductase/adrenodoxin increases with their E7. However, their cytotoxicity in mouse hepatoma MH22a and human colon carcinoma HCT-116 cells exhibited a poorly expressed dependence on E7. The correlations were significantly improved after the introduction of compound octanol/water distribution coefficient at pH 7.0 (log D) as a second variable. This shows that the lipophilicity of ArNO2 enhances their cytotoxicity. The inhibitors of cytochromes P-450, α-naphthoflavone, isoniazid and miconazole, and an inhibitor of DT-diaphorase, dicoumarol, in most cases decreased the cytotoxicity of several randomly chosen compounds. This shows that the observed cytotoxicity vs E7 relationships in fact reflect the superposition of several cytotoxicity mechanisms.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48753495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-19DOI: 10.6001/chemija.v31i3.4289
A. Kubiliene, M. Marksa, J. Baranauskaite, O. Ragažinskienė, L. Ivanauskas
3 Kaunas Botanical Garden of Vytautas Magnus University, 4 Ž. A. Žiliberas Street, 46324 Kaunas, Lithuania Cannabis is one of the oldest plants on earth, which is known and used for medical purposes. There are many articles on hempseed oil research in the scientific databases, while the antioxidant activity of Cannabis sativa L. herb extracts has not been extensively studied yet, to our knowledge. In the present study, antioxidant properties of different Cannabis sativa L. varieties from different regions of Lithuania were examined. Spectrophotometric FRAP (ferric reducing antioxidant power) and CUPRAC (cupric reducing antioxidant capacity) methods were used for determination. It was found that Cannabis sativa L. herb extracts possess antioxidant activity. The strongest antioxidant activity was evaluated in the Futura variety and the lowest in Manoica. The obtained results showed that a statistically significant (p ˂ 0.05) higher reductive power was determined by analysing the raw material by the spectrophotometric FRAP method. According to the hemp growth location in Lithuania, the highest TEAC values were estimated in the samples from the North region.
{"title":"Comparative evaluation of antioxidant activity of Cannabis sativa L. using FRAP and CUPRAP assays","authors":"A. Kubiliene, M. Marksa, J. Baranauskaite, O. Ragažinskienė, L. Ivanauskas","doi":"10.6001/chemija.v31i3.4289","DOIUrl":"https://doi.org/10.6001/chemija.v31i3.4289","url":null,"abstract":"3 Kaunas Botanical Garden of Vytautas Magnus University, 4 Ž. A. Žiliberas Street, 46324 Kaunas, Lithuania Cannabis is one of the oldest plants on earth, which is known and used for medical purposes. There are many articles on hempseed oil research in the scientific databases, while the antioxidant activity of Cannabis sativa L. herb extracts has not been extensively studied yet, to our knowledge. In the present study, antioxidant properties of different Cannabis sativa L. varieties from different regions of Lithuania were examined. Spectrophotometric FRAP (ferric reducing antioxidant power) and CUPRAC (cupric reducing antioxidant capacity) methods were used for determination. It was found that Cannabis sativa L. herb extracts possess antioxidant activity. The strongest antioxidant activity was evaluated in the Futura variety and the lowest in Manoica. The obtained results showed that a statistically significant (p ˂ 0.05) higher reductive power was determined by analysing the raw material by the spectrophotometric FRAP method. According to the hemp growth location in Lithuania, the highest TEAC values were estimated in the samples from the North region.","PeriodicalId":9720,"journal":{"name":"Chemija","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47689046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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